Fire alarm system



July 51960 c. L. TETHEROW FIRE ALARM SYSTEM 2 Sheets-Sheet 1 Fil d Jan. 15, 1956 INVENTOR. C/m/de L. 77ke/vw 2% Arm New 2 Sheets-Sheet 2 w m M 1 d m M o 3% m Q V 6 QQ L W qt \fimw I 1\& 6 1 air mi & M w w M KSM A s 6 A a July 5, 1960 c. TETHEROW FIRE ALARM SYSTEM Filed Jan. 1a, 1956 of which outside professional assistance will be summoned" ing abnormal temperatures or rates of temperature rise,

United States Patent 25"laims; (Cf. 340-413) The present invention relates to fire alarm systems designed for the protection of specific premises, which premises in any giveninstance may comprise, for example, a single building (e.g., a hotel, hospital or business establishment) or a cluster of rather closely integrated buildings (e.g., a college, manufacturing plant or military post).

In such a system. the primary objective quite naturally is to alert occupants of the protectedpremises in the event of fire and also to apprise the inangement or other appropriate personnel as to theportion of the premises in which the hazard exists, so that they may act speedily in combatting the fire and/ or guiding,v any evacuation-that may be necessary to protect life and property; Another object of my invention, however, is to provide facilities'by means automatically and immediately as by signalling the fire station headquarters of the community in or near which the endangered premises is located. c

To the latter end I provide at' the headquarters station a compact alarm panel to which the alarm system of any private party desiring this additional protection can be connected by means of a simple two-conductor linewhich, conveniently may be, for'instance, a leased telephone-line; An object of the invention, inother word's, isto' provide a single headquartersipanel capable of serving any desired. number of privatejsubscribers, which panel will'not only give the necessary a'larm' when the occasion arises but also will identify the subscriber whose premises is endangered.

Reverting to the installation at the protected premises, an object of the invention is to provide an alarm system for local personnel which is entirely self-sufiicient in the sense that it is in no way dependent uponthe'he'jadquarters station for any phase of its operation; According to the invention, the local installation comprises a small central-- ly located panel or cabinet containing all of the necessary components of the system except (1) the lines extending therefrom to different portions of the premisesfordetectand (2) the bells, horns or other alarms whichare tube operated for alerting personnel. This panel,; like the panel at the headquarters station, can be assembled wiredu and tested at the factory so that installation is reduced to a matter of completing the relativelysimple external circuitry which will in any event be determined by the layout of the premises to beprotected. a

It is a feature of the invention to provide a local panel capable of serving any desired number or external detection circuits and which can at any time quite easily and simply be made to accommodate additional external circuits if the premises should be enlarged. i V i To the end'that the local system, be entirely self-sufiicient, an object of the invention is to providethe panel Patented July 5, 1960 ice vention, thisis accomplished through the novel use of blocking valves (diodes or rectifiers) in certain alarm and supervisory circuits to eliminate relay contacts which otherwise would be required in these circuits. 7 Still another object of the invention is to supplement the supervisory functions of the local panel by providing for automatic over-all supervision at the remoteheadquarters panel; more particularly, it is one of my aims to provide the headquarters panel with means for maintaining constant automatic supervision over the various local panels connected thereto and in additionmaintaining the various connecting lines between the headquarters panel and the local panels under constant supervision to the end that said lines may be kept clear of all faults which would impair the giving of an alarm atthe headquarters station in the event of a fire at any one of the protected premises;

According to the invention, audible signals are utilized both at the protected premises and at the headquarters station for the purpose of alerting proper personnel whenever a fault of any kind arises in the circuitry of the system.- A useful feature resides in the provision of meansfor silencing the. audible: signal. at either location while a fault is being investigated and corrected. In this con-- nection, an. object of the invention is to safeguard against' human error occurring through failure to recondition the signal for operation when the trouble is cleared; this is accomplished either by automatically reconditioning the signal at the proper time, or by providing an automatic I reminder signal which will insure manual resetting.

With respect to the headquarters station, a collateral object of the invention is-toprovide an audible fire alarm signal which can be silenced when the fire fighting perwhich will remain operative to give alarms ifthe occasiorr arises, even in the face of unremedied circuit faults that.

might be expected to make the system ineffectual.

Finally,an important aim of the invention is to provide a, system having all of the foregoing features and advantages' but which is relatively inexpensive to manufacture and install.

Other objects, together with the features and novelty whereby the objects are achieved, will appear in thecourse of the following description of the invention. 'In thisdescription it will be assumed for the sake; of'simpl'icity: that the audible fire alarm to be sounded at the protected premises and at the headquarters station is'in each in stance a single bell, and that a single buzzer is utilized at each location 'to give an audible indication of the existence of, a circuit fault" which requires attention. This, of

course, should be understood merely to beexemp'lary of the audible signals which may' be used. As those versed in the art will appreciate, the. alarm signal may comprise a bell, a siren, a horn, or any desired combination of such sound emitters connected in parallel to operatesimultaneously; on. the other hand, the. fault signal may comprise a buzzer, a belL. a horn or the like, so long as the sound that produced iu,

emitted is easily distinguishable from the. case of a fire alarm.

In the accompanying drawings which form a part of the specification and are to be read in conjunction there- Fig. 2 is a schematic circuit diagram of a remote head- 7 quarters station which may be connected to one or more local stations of the kind illustrated in Fig. 1.

GENERAL DESCRIPTION Referring first to Fig. 1, it will be convenient for purposes of explanation to assume that this represents an installation at a hospital or other institution which occupies a single building or a cluster or rather closely integrated buildings under a single management. In the main office or other selected location on the premises a small cabinet or central panel is provided which houses all of the equipment shown in Fig. l with the exception of the external fire detection loops such as L1 and L2. There can be as many external loops as needed, each serving a different section of the premises, but for simplicity only two have been illustrated. Thus, in the case of a multi-story building the first floor would be assigned one fire detection loop (L1), the second floor another loop (L2) and so on; or different loops can be assigned to different wings of the same building or to different outbuildings in a cluster comprising a single institution or plant.

Each external fire detection loop, then, comprises a pair of conductors which extends from the aforementioned cabinet or central panel and after passing through its assigned portion of the premises returns to the panel. At different points along its length (for example, in different rooms of the building) the fire detection devices H1, H2, H3, etc., are located, each of these comprising a pair of normally open contacts which close responsive to the temperature rising above a predetermined value and/or responsive to an abnormal rate of temperature rise even in the range below that value. Such thermally actuated devices are, of course,-well known in the art. Any number of them can be connected to the same external loop in accordance with the requirements of a given installation, and the loop may also have connected thereto one or more manually operated pull boxes such as P1 and P2.

It will be noted that the external fire detection loop L1 has associated with it, in the central panel, certain equipment which is individual to that loop, namely:

As previously indicated, there is no practical limit to the number of fire detection loops that can be provided, but in the case of each loop there must be a similar set of relays, lamps, etc., individual thereto. Thus, external loop L2 is provided with:

Alarm relay A2 Supervisory relay S2 Alarm transfer relay ATZ Alarm lamp AL2 Supervisory lamp SL2 Valves V2, V4

all of which are connected to the conductors 40,. 41, 42,.

43 and 44 in precisely the same fashion as the corresponding equipment individual to loop L1. The same practice is, of course, followed in the case of each additional external fire detection loop with which the system is provided. 7 7

In addition to the equipment individual to'specific external loops, as aforesaid, the central panel contains the following equipment common to all of the loops:

Alarm bell AB Trouble buzzer TB Auxiliary supervisory lamp ASL Bell supervisory lamp BSL Pilot lamp PL Trouble lamp TL Master alarm relay MA Auxiliary supervisory relay AS Bell supervisory relay BS Master signal relay MS Trouble relay T Changeover relay CO Signal transfer relay ST Reset switch RS Trouble buzzer silencing switch TBSS Valves V5, V6 Emergency battery EP Trouble battery The local panel (Fig. l) at the protected premises is connected by means of a two-conductor transmission line 45, 46 to a remote main panel (Fig. 2) that may be located, for example, at the fire headquarters station for the municipality in which, or near which, the protected premises is located. Another local panel like that of Fig. 1 but serving a different premises may be similarly connected to the main panel via transmission line 45', 46'.

Attention is directed to the fact that the incoming transmission line 45, 46 has associated with it certain equipment individual to that line, namely:

Valves V7, V8, V11

The incoming transmission line 45, 46' has an iden tical set of relays (CV9, CA9, LR9), lamps (CAL9, CSL9) and valves (V9, V10, V12) individual to that line, all of these being connected to the common conductors 47, 48 and 49 in precisely the same fashion as the corresponding elements individual to incoming lines 45, 46. If there are other incoming transmission lines from additional local panels (and there is no limit to the number that can be accommodated by the central panel) it will be understood that each must be provided with similar individual equipment connected to the common conductors 47, 48 and 49 in the same manner; the back contacts (e.g., 82, 92) of the alarm relays associated with all of the various incoming lines are connected seriatim to the winding of the main alarm relay MAR as will be clear from the drawing. The main alarm relay is, of course, common to all of the incoming transmission lines and the same is true of the following corn ponents located at the'main panel:

Main alarm bell -'MAB Main trouble buzzer MTB Main alarm lamp MAL Main trouble lamp MTL Main pilot lamp MPL Main lock-in relay MLR Main change-over relay MCO Trouble relay TR Trouble silencing relay TS Trouble silencing switch 1 T SW Alarm silencing switch ASW Main reset switch MRS In both figures all manually operated switches are shown in. their normal position, and the heat detecting devices (H1, H2, H3, etc.) of Fig. 1 also are shown in i open or non-actuated condition, as is the case when they arernot exposed to elevated temperature or to an abnormal rate of rise in temperature. The contacts of the various relays are shown in the position they occupy when no external source of power is connected to either panel; and under that condition all of the lamps are extinguished and all of the audible signals are silent. With this preliminary outline, let us consider the operation of my system, beginning first with the local panel shown in Fig. 1.

Stand-by operating condition The local panel (Fig. l) is designed in normal use to receive its power from an outside source connected to terminals 36, 37. This, of course, can be a battery or a DC. generator; in most installations, however, it is more convenient to take advantage of the alternating current available at the protected premises via the commercial power mains, and supply same to a conventional full wave rectifier whose output is impressed upon terminals 36, 37 in the form of a DC. potential of the polarityindicated. Pilot lamp PL and the winding of change-over relay C0 are connected in parallel directly across these terminals so when the panel is thus energized, the pilot lamp is automatically lighted and relay CO is energized. Relay CO therefore operates closing its contacts 2 and 3.

Accordingly, conductor 43 now is energized positively over a circuit extending thereto from terminal 36 through are energized negatively over a circuit extending thereto from terminal 37 through contact 3 and conductor 51. The ensuing operations can conveniently be described with reference to the positive potential now existing on conductor 43 and the negative potential existing on con: ductors 42 and 44. I

From positive conductor 43 an obvious circuit extends through the alarm bell AB, conductor 53 and the winding of the bell supervisory relay BS to the negative conductor 44. The resistance of the supervisory relay coil is several times as great as the resistance of the alarm bell coil, .80 that 90 percent or more of the potential impressed on this series circuit appears across the relay coil'and only a small portion appears across the bell-a situation which, as will be seen presently, is duplicated'in the circuits for the other supervisory relays. While theresistance of relay BS'isf too high to permit thealarrn hell AB to operate in series-therewith, relay BS can and does operate in this circuit, opening its contact 35. r

'A second obvious circuit exists from positive conductor 43 through the winding of master signal relay MS, conductor 54 and winding of auxiliary supervisory relay AS to negative conductor 44. Accordingly, relay AS operates, opening its contact 34, but the resistance of its winding is too great to permit marginal relay MS to operate in series therewith so the contacts of the latter relay remain in the position shown. v

A third obvious circuit exists from positive conductor 43 through the winding of alarm relay A1, conductor 55, winding of supervisory relay S1, contact 18 andconductor 56' to the negative conductor '44; UponQbeing energized over this circuit, supervisory relay S1 operates opening its contact 19, but the resistance of itswinding is too great to permit the-marginal alarm relay A1 to opcrate in series therewith, so its contacts remain in the position shown. i

Relays S2 'and- A2, are energized in a' similar series circuit extending over conductors 57 and 58 but; as has just been described, only the supervisory relay S2 will 6 individually associated with other external loops like Li and L2 will be operated in similar fashion.

So long as the panel remains in stand-by operating condition as described, the only relays operated are CO and the various supervisory relays (AS, BS, S1, S2, etc.). The only lamp lighted is the pilot lamp PL. It should be noted, however, that the positive potential on conductor 43 is connected via a current limiting resistor R and contact 8 to conductor 45 of the outgoing transmission line, while the opposite conductor 46 of the transmission line is energized negatively via contacts 6 and 10 from the negative terminal 37 of the power supply. The purpose of this will be described presently.

Alarm conditions Let it now be assumed that a fire begins inthe section of the protected premises which is served by external loop L1, and more particularly in the region near the heat detector H2. By closing its contacts this detector places a short circuit condition on the winding of supervisory relay S1 thereby increasing the flow of current through the alarm relay A1. As a result, the supervisory relay releases and the alarm relay operates; the latter imoperate in this circuit," relay A2 remaining in non-operated condition as shown due to the higher resistance either w nd ng of r lay AnYmhersHPeIvisQry relays mediately closes a locking circuit for itself which extends from positive conductor 43 through the winding of relay A1 and contact 14 to the negative conductor 42. Accordingly, alarm relay A1 will remain operated even if the contacts of the heat detector H2 should subsequently reopen, or even if there should be some interruption in the continuity of one or both conductors of the external loop L1 as a result of the fire.

Upon operating, relay A1 completes an obvious circuit extending from positive conductor 43 through alarm lamp AL! and contact 15 to negative conductor 42, whereby thelamp is lighted; the same contact completes the following circuit for energizing the master alarm relay MA: positive conductor 43, conductor 59, winding of relay MA, conductor 40, valve V1 and contact 15 to negative conductor 42.

(It should be noted perhaps at this point that the valve V1 and the corresponding valves V2, etc., have very low resistance to current fiow in the direction just mentioned but very high resistance to current flow in the opposite direction. Accordingly, though a circuit exists from positive conductor 43 through alarm lamp ALZ, valve V2, conductor 40, valve V1 and contact 15 to negative conductor 42, valveVZ blocks the flow of current in this circuit, preventing alarm lamp All from lighting; the same is true of the alarm lampshindiyidual to any additional external loops similar to L2.)

Upon operating, relay MA immediately completes a locking circuit for itself, which extends from positive conductor 43 via conductor 59, winding of relay MA and contact 33 to negative conductor 42. By closing contact32, relay MA short-circuits the winding of relay AS (negative conductor 44, winding of relay AS; contact 32, conductor 42 and switch RS back to conductor 44) and at contact 31 a similar short circuit is completed for the winding of relay BS. Relays AS and. BS therefore releas e;--at contact 34 the former now completes an 0bvious circuit (positive conductor 43, lamp ASL and contact 34 to negative conductor 42.) for lighting lamp ASL' while at contact 35 a similar circuit is. completed for lighting lamp BSL. v

The short circuiting of relay BS increases the current flow through alarm bell AB, and same is now fully energized over a circuit extending from positive conductor 4-3 through the alarm bell and contact 31 to negative conductor42. Similarly the short-circuiting of relay AS at contact 32'increases the current flow through'master signal relay-MS and same is fully energized, so that it opens contacts 6 and 8 and closes contacts 7 and 9.. Accordingly, "conductor 45 which previously had positive potential connected thereto now is energized negatively over a circuit extending from negative conductor 42 through contact 32, conductor 54 and contact 9; and conductor 46 which previously was energized negatively now has positive potential connected thereto over a circuit extending from positive terminal 36 of the power supply through contact 2, conductors 59 and 43, current limiting resistor R and contact 7. In other words, the operation of relay MS results in a reversal of the polarity of outgoing conductors 45 and 46 of the transmission line ex tending to the central headquarters panel (Fig. 2).

As previously mentioned, supervisory relay S1 which is individual to the external loop Ll already has released due to the short circuit condition placed thereon by closing of the heat detector contacts H2. Consequently, relay contact 19 is closed, completing a circuit which extends from positive conductor 43 through the winding of relay ATI and lamp SL1 in parallel, conductor 60 and contact 19 to negative conductor 42. Supervisory lamp SL1 therefore is lighted, and relay ATI is energized but the latter serves no useful purpose at this point. The closing of contact 19 also completes the following circuit for energizing trouble relay T: positive conductor 43, winding of relay T, conductors 61 and 41, valve V3 and corn tact 19 to negative conductor 4-2,. (Although a circuit exists from positive conductor 43 through .supervisory lamp SL2, valve V4, conductor 41, valve V3 and contact 19 to negative conductor 42, it will be understood from the earlier description that valve V4 blocks the current flow in this circuit so prevents the supervisory lamp SL2 from lighting.)

Upon operating, relay T immediately completes a locking circuit for itself which extends from positive conductor 43 through the winding of the relay and contact 12 to negative conductor 42. It also opens contact 16) (which serves no useful purpose at this point) and closes contact 11; the latter completes a circuit which extends from the positive terminal of the trouble battery TP via conductors 50', t) and 43 through contact 11, conductor 62, the upper blade of switch TBSS and trouble buzzer TB to the negative side of battery TP. The trouble bell is energized over this circuit, and inasmuch as the trouble lamp TL is in parallel therewith, it also is lighted.

Accordingly, it will be seen that as a result of the closing of heat detector contacts H2, the alarm bell AB and trouble buzzer TB are both placed in operation, and lamps ASL, ESL and TL are lighted, these being all of the lamps which are common to the various external fire de tection loops L1, L2, etc. At the same time, for-the purpose of identifying the portion of the protected premises in which the fire has started the lamps ALI and SL1 individual to the fire detection loop L1 which serve that portion of the premises are also lighted. The lamps (such as AL2 and SL2) individual to other external fire detection loops of course remain unlighted. The operations which have been described as the result of the closing of heat detector contact H2 would of course be duplicated if any other heat detector in loop Ll were actuated, or if one of the manual pull boxes Pl associated with the same loop were operated.

If the foregoing alarm signal condition were initiated by a heat detector or pull box on another external loop, such as L2, the operations would be the'same except that the lamps AL2 and SL2 individual to that loop would be lighted rather than the lamps AL]. and SL1. In the case of any alarm, the alarm relay (A1 in the case of external loop L1, and A2 in the case of external loop L2) remains operated over its own locking circuit, as do also the master alarm relay MA and trouble relay T, until such time as the panel is manually returned to normal condition as hereinafter described. Consequently, the audible signals will continue to sound and the lamps will remain lighted as outlined above until conditions warrant manual resetting of the panel.

Resetting the panel after a fire alarm Let it be assumed that after a fire alarm has been initiated by the external detection loop L1 the fire has been extinguished and the heat detector (say, H2) which initiated the alarm has been replaced, or reset to open condition. To restore the panel to its normal stand-by condition so that it will be ready to reoperate in the event of another fire, it is only necessary to manually operate the self-restoring, normally closed reset switch RS which, upon opening, removes from conductor 42 the negative potential which was previously supplied thereto via conductor 51. It will be understood from the previous description that alarm bell AB, lamps ASL, BS L, AL1 and SL1 and relays MS, T, MA, A1 and ATI all depend upon the negative potential on conductor 42 for their continued operation; accordingly, removal of potential from this conductor brings about the immediate release of these five relays, as well as extinguishing the four lamps and causing the alarm bell AB to cease operating.

Moreover, the opening of switch RS removes the shortcircuit condition therefore existing on the windings of supervisory relays AS, BS and S1 so that these relays now reoperate over the same circuits as described earlier under the heading Stand-by operating condition. Upon release of relay T, contact 11 opens to interrupt the previously described circuit for trouble buzzer TB and trouble lamp TL, so that this buzzer also ceases its operation and the associated lamp is extinguished.

The release of the master signal relay MS restores its contacts to the position shown, thereby restoring the outgoing conductors 45, 46 to the same polarity that existed' thereon prior to initiation of the fire alarm. With reclosing of the manual switch RS, the panel is fully restored to stand-by operating condition and until such time as another fire hazard may arise, it will remain in this condition, unless in the meantime some circuit difficulty arises which should receive attention in order to insure continuity of protection. Let us now give attention to the matter of supervising the system to guard against the possibility of faulty operation.

Supervisory operation Naturally, in installing a fire alarm system in a given premises, it is not to be anticipated that fires will occur with any frequency; on the contrary, a fire is an emergency which may occur only once in many months, or once in many yearsor perhaps never. While awaiting that possible emergency, the system must maintain continuous vigilance, day in and day out, month after tedious month, during which time, if it is ready to give the proper alarm when and if the need arises, its condition can best be described as a state of suspended animation. It simply remains, in other words, in the stand-by operating condition described earlier.

Having in mind that except for infrequent and perhaps cursory inspections, the apparatus is likely to receive little attention during these long .periods of inactivity, I make the system self-supervising to the end that it will give both audible and visual warnings in the event that it requires attention in order to insure its proper operation in the event of a fire. Such warnings are given to indicate the following abnormal fault conditions, any one of which may manifest itself as a source of potential trouble in the system during a period of standby operation: a 1

(1) Main power supply failure.

(2) Open circuit in one of the externalfire detection loops L1,'L2, etc.

(3) Open circuit to alarm bell AB. (4) Open circuit to coil of master signal relay MS. Considering these faults in the order named, it will be' evident that if there is a failure in the main powersupply connected to terminals 36, 37, pilot lamp PL will be immediately extinguished and change-over relay CO will be de-energizedopening contactsl and 3 and relay T, conductor 69, one of the valves V5 or V6 and through contact 34 or 35 (depending upon which relay has released) to negative conductor 42. RelayT operates over this circuit and by closing contact 11 causes the trouble buzzer TB to operate and the trouble lamp TL to light as described hereinbefore. If it is the bell supervisory relay which has released an obvious circuit over contact 35 also will exist for lighting bell supervisory lamp BSL; if, on the other hand, it is the auxiliary supervisory relay AS which has released, an obvious circuit will exist over contact 34 for lighting the auxiliary supervisory lamp ASL. The lighting of one or the other of these lamps naturally will identify the nature and location of the trouble so that it can be repaired.

Trouble buzzer silencing Whenever the trouble relay T operates due to any of the fault conditions outlined above, a visual and audible trouble signal results due to the circuit extending from the positive terminal of trouble battery TP via conductors 50', 50 and 43, contact 11, conductor 52, the upper blade of switch TBSS and thence in parallel through trouble lamp TL and trouble buzzer TB back to the negative side of battery TP; Simultaneously therewith, one or more of the supervisory lamips ASL, BSL, S1, S2, etc., will be lighted to 'assist'the service man in locating the source of the trouble. 7 While he is doing this and making the necessary' repair, the trouble buzzer TB can be silenced by manually reversing the double throw switch TBSS. When this is done, the lower blade of the switch connects the trouble lamp TL directly across the trouble battery TP so that it remains lighted. At the same time, the following circuit is completed over the upper blade of the switch: positive terminal of trouble battery TP, conductors 50', 5t) and 43, cont-act 11, the upper blade of switch TBSS and the winding of signal transfer relay TS back to the negative side of'the trouble battery. 'Relay ST operates over this circuit, opening its contact 5 so that the trouble buzzer TB now is silenced. Until the switch TBSS is restored to normal position, the lighted trouble lamp TL serves as a constant reminder that there is an abnormal condition requiring correction.

Should the faulty circuit conditions be corrected before the trouble buzzer silencing switch TBSS is restored to normal, the panel will be reset by momentarily opening reset switch RS and this will allow trouble relay T to release. Opening. of contact 11 will interrupt the aforementioned circuit for signal transfer relay ST, so it also releases closing its contact 5. As a result, a circuit is completed from the positive terminal of trouble battery TP over conductor 50', the lower blade of switch TBSS, contact 5 and trouble buzzer TB back to the negative side of the trouble battery. Accordingly, the buzzer will now sound to signify correction of the difficulty and will continue to. do so until the double throw switch TBSS is restored to normal position as shown, whereupon the circuit for trouble buzzer TB and trouble lamp TL will be opened, causing the former to be silenced and the latter to be extinguished.

Advantage of the same feature can be taken if the fault v in question is the failure of the main power supply connected to terminals 36 and 37. As previously mentioned, when this occurs, the trouble buzzer and trouble lamp are energized by. closing'of contact 1 on relay CO. If during the interval that the trouble is being investigated and corrected, switch TBSS is reversed in position, it completes a circuit as before for maintaining trouble lamp TL lighted, and it also completes the following circuit for energizing relay ST: trouble battery TP, conductor 50, contact 1, conductors 63 and 62, the upper blade of switch TBSS and the winding of relay ST back to the negative side of the'trouble battery This again opens contact 5 and by so doing interrupts the circuit to the trouble buzzer. If power now is restoredto the terminals36, 37, changeover relay CO will reoperate, opening contact 1 and thus 12 interrupting aforementioned circuit for the signal transfer relay SP. Closing of contact 5 therefore re-energizes the trouble buzzer as previously described and will cause it to continue to operate until the manual switch TBSS is restored to normal position.

It will be evident from the foregoing that the local panel shown in Fig. l is a complete fire alarm system in and of itself. In the case of a fire the system will give appropriate audible and visual signals for alerting the local personnel so that they may take immediate action to deal with the situation; and in the meantime if any circuit difiiculty should arise in the system itself it again will call attention thereto by appropriate audible and visual signals so that local personnel will be apprised of this difliculty. While the local panel is self-sufficient in these regards, it often is desirable to supplement the protection afforded thereby in the manner which now will be described with reference to Fig. 2.

CENTRAL HEADQUARTERS STATION Stand-by operating condition As was true in the case of the local panel (Fig. l) the central panel' (Fig. 2) is designed under normal conditions to receive its power from an external source connected to terminals 38 and 39. The main pilot lamp MPL and main change-over relay MCO are connected directly across these terminals and accordingly when the panel is thus energized the lamp immediately lights and relay MCO operates closing its contacts 87 and 88. Accordingly contact 87 causes conductors 64 and 48 to be energized negatively from the potential on terminal 39 while contact 88 causes conductors 65 and 47 to be energized positively. Therefore a circuit is completed from negative conductor 64 through the winding of main alarm relay MAR and the back contacts (e.g., 82 and 92) of all individual central alarm relays back to the positive conductor 47. Energized over this circuit, the master alarm relay MAR operates and opens its contact 99.

It will be recalled from the description previously given that when the local panel (Fig. l) is in stand-by operating condition it applies positive potential to con ductor and negative potential to conductor 46. In the central station (Fig. 2) this causes current to flow through the central vigilance relay CV1 and valve V7; valve V8 under this condition prevents the flow of current through the central alarm relay CA1. Accordingly only relay CV1 is operated, opening its contact 81. The same will be true, of course, of the relays (such as CV9 and CA9) individual to transmission lines extending to other local stations similar to that shown in Fig. 1.

Accordingly under stand-by operating conditions at the central station all central vigilance relays CV1, CV9, etc., are operated and relays MAR and MCO also are operated; the only lamp lighted is the main pilot lamp MPL.

Alarm conditions Should a fire alarm occur at the local panel (Fig. l) the polarity of the potential connected to conductors 45 and 46 will be reversed as described hereinbefore. Upon such reversal valve V7 blocks the flow of current through relay CV1 while valve V8 now permits current to flow through the winding of the central alarm relay CA1. Relay CV1 immediately releases closing its contact 81 while relay CA1 operates opening contact 82 and closing contact 83. The opening of contact 82 interrupts the previously described circuit for relay MAR which therefore releases closing its contact 99. Therefore, a circuit now exists extending from positive conductor through contact 99 and in parallel through the winding of relay MLR, the main alarm bell MAB and the. main alarm lamp MAL to negative conductor 64. The main alarm bell MAB thus is placed in operation and the main alarm lamp MAL is lighted; the main locking relay enesir r 13 a MLR also operates over this circuit to close its contact 98, but for the moment this serves no useful urpe'se,

Upon operation of the central alarm relay CA1 the closing. of contact 83 completes a circuit which extends from negative conductor 48 through conductor 66, thence in parallelthrough lamp CALI and thewinding of relay LRI, contact 83, conductor 67 and contact 9 2 h'ack to the, positive conductor '47. The central alarm lamp CAL1 individual to the transmission line 45, '46, therefore, is lighted and relay LRI upon operating closes contact 84 to complete an obvious locking circuit for itself. At the same time contact 85 is opened interruptin'g the circuit for central alarm relay CA1 which immediatelyde-energizes and restores its contacts to the position shown. Despite the opening of contact 83 lamp CALI and relay LRl 'reinain energized over the locking circuit completed at contact 84. The closing of contact 82, however, causes relay MAR to re-energ'i ze, opening its contact 99; contact 98 "ne is effective to maintain relay MLR, the main al'a'rm bell MAB and the, main alarm. lamp MAL'ener'g'ized .despitethe opening of contact 99.

All of the operations thus far described have taken place as a result of the momentary operation of central Y alarm relay CA1 which, it will be remembered, was initiated by the reversal of polarity on conductors 4'5 and 46. The release'of central vigilance relay CV1 occasion'ed by such reversal closes contact 81- and thus cornpletes an obvious circuit extending from positive conductor 47 through contact 81 and central supervisory p CSL1 back to ne'gative conductor 48. Thi lamp,

therefore, isals'o lighted. the same a circuit is completed from positiveconductor through contact 81, valve V11 and the winding oi trouble relay TR back to negative conductor -48, Relay TR operates and by closing its contact 20, completes A an obvious circuit connecting the main trouble battery. MTP to the main trouble lamp MTL so that the latter is' energized. The main trouble buzzer MTB is connected in parallel with this lamp by contact 97 so it also is placed inoperation.

Although a circuit now exists which extends from positive "conductor 47 through contact 81, valve V11, conductor 49, valve viz and lamp CSL9 back to negativc conductor 48, it Will be understood from the earlier discussion that valve V12 bloclis the newer current over this circuit and, thereroregprevems lamp CSL9 from lighting. Accordinglyonly'th'e lamps individual to the incoming line '45, 46 1, 13., CSL1 :ahfd CALT) will be lighted to identify, sofar as the 'centra'l stationis concerned, the premises which initiated thealarm. The main alarm lamp MAL and niain trouhl'e lamp MTL will, of course, also be lighted'and the main alarm bell MAB and main trouble buzzerMTB will h'ejene'rgizedto give audible signals for the purpose of alerting personnel at the central station. t V

If an alarm is initiated by the local station connected to the transmission line 45, 46'. rather than by the one connected to transmission line 45, 4'6,"the'operations will -beexactly as have been described except that lamps CSL9 and CAL-9 willbe lighted rather than lamps CSL1 and CALI; lock-in relay LR9 will be operated rather than inii uiclr-succession on thetransmission lines associated with two ormore local'panels, the pair oflamps individual to each of these lines will 'be lighted in the manner line serving a premises "at which' there'is no fire will remain dark.

. relay LR1; and'central vigilance relay CV9- wil1 be deenergized rather than relay :CVl. "Should alarms occur 1 i4 Silencing zhe audible signals at central headquarters station Let us assume once more than an alarm has come in' on the transmission line 45, 46 and that as a result the main 'alann bell MAB and main trouble buzzer MTB are in operation. The alarm bell may be silenced by momentary manual operation of the normally closed selfrestoring switch ASW. When thisis opened it interrupts the circuit for the main lock-in relay MLR which releases, opening its contact 98; the latter interrupts the circuit of the main alarm bell MAB and the main alarm lamp MAL so that both are de=energized. The switch ASW now may be permitted to return to closed position without producing any fur-theft elfect.

To silence the main trouble buzzer the operator needs only to momentarily close the normally open self-restoring switch TSW. When this is done it completes a'circuit extending from the positive terminal of the main trouble battery MT P through conductor 65, contact switch TSW and the winding of the trouble silencing relay TS back to the negative side of the main trouble battery Relay TS energizes overthis circuit and immediately completes a locking circuit for itself at contact 96 so that it will remain operated when switch TSW subsequently is permitted to open. At contact 97 the circuit for the main trouble buzzer MTB is opened so that it ceases operation; it'should be noted, howeventhat the main trouble lamp remains lighted by virtue of the circuit existing thereto at contact 90.

Should thefi're alarm condition at the local panel (Fig. 1) now clear, the polarity of conductors 45, 46 will be restored to normal causing the central vigilance relay CV1 to reopera te. By opening contact '81 this relay will interrupt the circuit for the central supervisory lamp CSL1 and the trouble relay TR. Accordingly the lamp is extinguished While the relay releases. Contact 96, therefore, is now opened which will extinguish the main trouble lamp MTL and interrupt the circuit for the trouble silencing switch TS which also de-energizes'.

When lamps M11 and CSL1 go out as just explained it is an indication to the operator at the central station that the alarm conditions have cleared and he can, therefore, reset the panel. To do this he momentarily opens the self-restoring main reset switch MRS which interrupts the circuit for lock-in relay LRl and lamp CAL1; accordingly these are de-energi'zed and, due to the opening of contact 84, will notr eop'erate when switch MRS is permitted to reclose. The central panel, thus, is fully restored to normal stand-by operating condition.

y Let it now'be assumed that a fire alarm condition has been "initiated on transmission line '45, 46 and that by momentarily operating switches ASW and TSW the operator has silenced the main alarm bell MAB and the main trouble buzzer MTB. As previously noted, the main trouble'lamp-MTL still'is lighted and so are the lamps CALI and CSL1 individual to the incoming transmission line 45, Should an alarm condition now occur-on another incoming transmission line (say 45', 46) the reversal of polarity on these conductors will cause relay CV? to release and at contact 91 complete a circuit for lighting the'associated supervisory lamp CSL9. At the same'time'relay CA9 will be momentarily energized and at contact 93- complete a circuit for lighting lamp CAL9 and eriergizing the lock in relay LR9. Opening of contact 92'causes the master alarm rela y to release, closing contact 99., so that the circuits once more are completed for, energizing 'the'master lock-in relay MLR, themain alarm bell MAB and the main alarm lamp MAL. It isto be noted, in other Words, that even if these have been silenced by the opening of the switch ASW after an initial alarm, they will reo'perate responsive to a second 7 ala'rm condi tion on another incoming transmission line ifsuch should occur before thejalarm conditionon 'the 15 other operations which take place as a result of the second alarm will be clear from the description already given.

Supervisory operation at central headquarters station One of the valuable features of the invention resides in the arrangement of the circuits at the central station to provide a visible and audible signal in the event of a trouble or fault condition developing at any of the local stations serviced thereby, or in the event of a break of short-circuit in the connecting lines from the local to the central station.

As has been explained in connection with the discussion of the supevisory operation of the local station illustrated in Fig. 1, any trouble or fault condition developing in the circuits therein immediately energizes trouble relay T thus initiating operation of trouble buzzer TB and trouble light TL to signal the existence of the unfavorable condition. Concurrently with the signal at the local panel, contact is opened by relay T with the effect that the negative potential is removed from conductor 46 of the transmission line. As a result, current no longer flows through the winding of vigilance relay CV1 at the central headquarters (Fig. 2); the relay releases and contact 81 closes, thereby completing a circuit from positive conductor 65, through conductor 47, contact 81, and central supervisory lamp CSLl to negative conductor 48. At the same time relay TR is energized, being in parallel with lamp CSLll in a circuit including valve V11, and contact 9% therefore is closed. This completes an obvious circuit through main trouble lamp MTL and main trouble buzzer MTB to provide an immediate indication of difficulty somewhere in the over-all system. The illumination of lamp CSLll localizes it to the station served by lines 45 and 46 and an investigation can be made and the fault or trouble corrected.

It should be evident that the occurrence of a fault or trouble condition as described above will have no effect on the alarm circuits of the central station and that neither the central alarm lamps CALL CAL9, etc, the main alarm lamp MAL nor the main alarm bell MAB will be energized. These elements remain in standby condition ready to receive a fire alarm. If while a fault exists at the station served by transmission line 45, 46, such an alarm should come in on line 45, 46', the resultant operation of alarm relay CA9 as heretofore described will light the associated central alarm lamp CAL9 and energize the main alarm bell MAB and main alarm lamp MAL, all in the manner set forth. As a matter of fact, the same will occur even if a fire should begin at the station where the fault exists. In other Words, referring to Fig. l and assuming that trouble relay T is operated so that negative potential is removed from conductor ,6, if master signal relay MS should now be energized due to the occurrence of a fire before the fault is cleared, it

will cause conductor 45 to be energized negatively and conductor 46 to be energized positively as already explained, whereupon central alarm relay CA1 (Fig. 2) will be operated to bring in the alarm in normal fashion at the headquarters station.

It will be noted also that the arrangement at the cen tral station is such that the trouble signal will be given at buzzer MTB and lamp MTL in the event of either a break of a cross in one of the transmission lines 45, 46, or 45', 46', etc. In either case, the vigilance relay CV1, CV9, etc., associated with the faulty transmission line will be de-energized, thus closing contact 8 91, etc., and initiating operation of trouble relay TR and the trouble signals MTB and MTL as hereinbefore described, along with the supervisory lamp (CSLl, CSL9, etc.) individual to the faulty line. vclo-ps between the conductors of a given transmission line, the resistor R at the local station limits the amount of currentto a safe value.

Main power failure at any of the local stations also Where a cross or short circuit de-- initiates activity of the trouble signals MTL and MTB at the central station. Immediately the potential is removed from terminals 36 and 37 (Fig. 1), the negative potential is removedfrom transmission line 46; this is not remedied by the bringing into play of the emergency power system. Vigilance relay CV1 (Fig. 2) is therefore de-energized and the closing of contact 81 sets in operation the trouble signals as hercinbefore explained. The central supervisory lamp CSLl is also energized and provides a means of determining the particular station where the power failure has taken place.

The supervisory circuits at the central station also monitor the central stations own power supply, and provide an immediate signal should there be a failure. If there is a failure in the main power supply connected to terminals 38 and 39, main pilot lamp MPL will be immediately extinguished and change-over relay MCO will be de-energzied opening contacts 87 and 88 and closing contacts 86 and 89. With the closing of contact 89, a circuit is completed from the positive terminal of the trouble power supply battery MTP through conductor 65', contact 89, contact 97 and the trouble buzzer MTB back to the negative terminal of the trouble battery; consequently, the buzzer MTB sounds an audible alarm, and inasmuch as main trouble lamp MTL is in parallel with the buzzer, it also is lighted.

At the same time the panels emergency battery MEP is substituted as a source of temporary power for maintaining conductor 47, 48 and 49 energized at the same potential that existed thereon before the failure of the external power source. More specifically, the positive side of battery MEP is connected via conductors 65' and 65 to the conductor 47 while the negative side of the battery now is connected via contact 86 and switch MRS to supply negative potential to conductors 48 and 49. Accordingly, while the trouble buzzer is calling attention to the existence of a fault which requires correction, the central station is otherwise maintained in standby operating condition ready to signal the existence of a fire condition, should one arise before the fault is corrected.

While the failure of the regular power supply is being investigated and corrected the trouble buzzer MTB can be silenced by momentarily closing switch TSW; this completes a circuit from the positive terminal of battery MTP through contact 89, switch TSW and the winding of relay TS to the negative terminal of battery MTP whereupon relay TS operates to open'the circuit of the buzzer at contact 79. At contact 96 relay TS completes a locking circuit for itself so will remain operated independently of switch TSW as previously described. Although the trouble buzzer now is silenced, the trouble lamp MTL remains lighted as a reminder of the existence of the fault. When the power supply is restored to terminals 38, 39, relay MCO will, of course, reoperate and the main pilot light MPL will again be lighted. By the opening of contact 89, the circuit for trouble lamp MTL is interrupted and the circuit for relay TS also is interrupted so that it will return to normal position.

Likewise, if the main trouble buzzer is placed in operation as a result of the energization of trouble relay TR (due to a fault existingin one of the local stations con nected to the transmission lines 45, 46 or 45, 46, etc.) the trouble buzzer may be silenced by momentary operation of switch TSW. As previously described, this completes a circuit from the battery MTP over contact 90 and switch TSW for energizing relay TS which thereupon interrupts the circuit for the trouble buzzer while the trouble lamp MTL remains lighted. When the faults cleared, relay TR will release and by opening contact 90 this interrupts the circuit for lamp MTL and relay TS so that the trouble signaling components are restored to normal condition. 1

From the foregoing it will be seen that this invention is one well adapted to attain all of the ends and objects a gkQnQS Q Sfim ci c ts hav n ndi idua i tarnorma WOIZ I -L i nw l s QhF 'QPPQSliG-WP mina c sa i se I meteor and alve- 1 a s miam aas operat e t hereinbefore set forth together with other advantages which" are obvious and which are inherent to the apparatus.

Inasmuch as many possible embodiments of the invention may be made without departing from the scope thereof, it is to be understood that all matters herein set forth or shown in the accompanying drawings are to be inter: preted as illustrative and not in a limiting sense.

For example, while I prefer to provide a central headquarters station such as shown in Fig. 2'in order to obtain dual alarms and dual supervision, such is not absolutely necessary because, as pointed out herein-before, each local station suchtas shown in Fig. is self-sujflicient. It will, in other words, give local personnel appropriate audible and visual signals'in the event of a tire and in the event of any fault in the circuit; its operation will be the same regardless of whether or not a' remote headquarters station is connected to the outgoing transmission line 45, .46. It will be understoodftliat if there is no headquarters station in the system, the master signal relay MS serves no useful actr ss and can be tt d as c n l its supervisory relay AS and the associated supervisory lamp ASL and valve V5. Likewise, contact 32 can be omitted from relay MA and contact 10 omitted from .rel'ay T. However, in the'interest of standardizing the manufac ture of local: panelssuch as Fig. 1, it usually is desirable to provide these components against the possible future 7 addition of a headquarters station (Fig, 2) to the system. s

It will of. coursevbe understood that certain features and snbcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by andits within the scope of the appended claims.

Having thus described my invention, I claim;

1. In a Zoned alarm system, a sourceof ,D.C. potential, a conductor common to all of the zones, a difierent signal. circuit for each zone, each S idcircuitcompr-ising alamp'inesenies with a ,unidirection ,current flow valve, the valves invall of said circuits beingp'oled in the same sense with respect tothe lamps in said circuits, the lamp end of each circuit being connected to ,one terminal of said source and the valve end of ,each cireuit beingconnected to said common conductor 'ivlaereby all of said circuits are in paralle1,.each said circuit having-individual thereto a normally open .contacttor connecting theopposite terminal of saidsource toythat circuit at a pcint' intermediate the lamp andthe: valve in thaticircuit,gone-controlled means for closing anyoneaof saidcontac s,.}a device common to all of said zones and aci lqdjitforienergi-zi-ng said device from said source: responsive to the closing: of any of said contacts, said as circuit including the closed contact and said-common conductor,

2. In a zoned alarm system havingipontionsindividual to the-respective zones and other portions common'to-all of the zones, asource of 13:6; potential, a conductor common to. allot the zones, a signal cir commonto all of said zones, each zone alsohavling l ndividual signal circuit, said common circuit andrsaid individual circuits each" comprising a lamp in: series with a unidirectional current flow valve, theI valves-in all of said eircuits being poled-in. the same sense wizth respectwt :the-lamps in said circuits; the'lanip end' of aehacircui heingzconnectedi to. one terminal-(of. Sflidn HIQC ,%HQ thB- V&IY6 ,end ofeach.circuiobeingzconnected'towsaidieoingrnonmonductor whereby alliofisaid: circuits are in parallel, -;a' normally open contact? tor connectingythe .oppcsiteqend of said source to said common circuit at point-intermediate the lamp vhlve therein, operative toclose visory circuit for each zone, each of said circuits com prising a lamp in series with a unidirectional current flow valve, the valves in all of said circuits being po'led in the same sense with respect to the lamps in said cir= :cuits, the lamp end of each of said circuits being connected to one terminal of said source of potential, the opposite end of each alarm circuit being connected to one or" said common conductors whereby all of said alarm circuits are in parallel, the opposite end of each supervisory circuit beingconnected to the other common condue-tor whereby all of said supervisory circuits are in parallel, each alarm circuit having anormally open consaidlcontacttresponsi-veto a fault ineazportiontofnthez'sys- I I temewhich issccmm wa l-19 s id z es; sas

eto

c tarcia -iat rm d a close diiferent ones of said last contacts responsive to tact for connecting the opposite terminal of said source to that circuit at a point intermediate the lamp and valve in that circuit, zone controlled means for closing any one of said contacts, a master alarm device connected to said one conductor and energized thereover from said source responsive to the closing of any one of said contacts, each supervisory circuit also having a normally open contact for connecting said opposite terminal of said source to that circuit at a point intermediate the lamp and valve in that circuit, zone controlled means for closing any one o sa a tcont t a d a master oub d v e conn ct d to sa on n u tor an ene gize the eo e twi sa d s ur e e po s e to' t e clo ng of ny on Q sla jdla t c ac 7 v 4.11;; an allarrri y e of t c racter de c ib d, a

source of DC. potential, a plurality of d'etec i'Qll circuits,

a master alarm device common to said detection circuits, ,a plurality of individual alarm circuits corresponding respectively to said detection circuits, each alarm circuit comprising an individual alarm device in Series .With .a unidirectional current flow valve, the valverendofr each alarm circuit being connected to one terminal. of said master alarm device, the opposite end of reach alarm c'ircuit and the opposite terminal of said master alarm device being connected to .one terminal vof said source pr potential each alarm circuit having a normally open contact for connecting the opposite terminal of said source to that circuit at a point intermediate the alarm device and valve in that circuit, means for closing the con-tact individual to any particular alarm circuit responsive to an abnormal condition in the detection circuit corresponding to that alarm circuit, and the valve in each alarm circuit being so poled as to permit current to .flow throughsame and said master alarm device in series :responsive to the closing of the contact associated with that circuit.

5. In an alarm system of the character ,described, .a plurality of detection circuits, a'pair of conductors common to said circuits, a plurality of identical alarm circuits connected in bridge between said conductors whereby said alarm circuits are in parallel with one another, said alarm circuits corresponding respectively to said detection circuits, a master alarm device, a' source ofiDJC. potential 'having one terminal connected to one of said conductors and also connected through said and said other conductor a unidirectional current flow 'the protected premises outside the panel and then returns to the panel, the portion of said line outside said panel being bridged by one or more normally open contacts capable of being closed to initiate an alarm, the coil of said supervisory relay normally being connected in bridge to said line at one end thereof, the other end of said line having one conductor thereof connected to one terminal of said source of potential and the other conductor con- .nected through the winding of said alarm relay to the .opposite terminal of said source, said supervisory relay normally being energized over said line from said source and said alarm relay being marginal whereby it cannot operate in series with said supervisory relay, a device in said panel controlled by said supervisory relay so as to operate responsive to the release of said supervisory relay for any reason, and means controlled by said device upon operation to disconnect said supervisory relay from said one end of said line and to connect together within the panel the opposite ends of each conductor of said line.

7. In a zoned alarm system of the type wherein an alarm condition in any zone causes the selective actuation of zone-identifying means in such manner as to register the identity of the zone in which said condition exists; the improvement which comprises, a first station having a trouble relay and an alarm relay common to all zones, means for operating said trouble relay responsive to a fault condition in any zone, means for operating said alarm relay responsive to an alarm condition in any zone, a second station remote from said first station but connected thereto by a two-conductor transmission line, a pair of oppositely polarized relays at said second station connected in bridge to said line, a source of DC. potential at said first station normally connected in bridge to said line to energize a particular one of said polarized relays, means at said first station for interrupting said last connection responsive to operation of said trouble relay, and other means at said first station for reversing the connection of said source to said line responsive to the operation of said alarm relay thereby to energize the other polarized relay.

8. A system as in claim 7 wherein each polarized relay comprises a relay having its winding in series with a unidirectional current flow valve.

9. A system as in claim 7 having a pair of alarms at said second station, a circuit for operating one of said alarms responsive to release of said particular one of said polarized relays, and a circuit for operating the other alarm responsive to energization of the other polarized relay.

10. In an alarm system as in claim 7, a contact so controlled by said particular polarized relay that said contact is open whenever the relay is energized and closed whenever the relay is released; a series circuit comprising a source of potential, a lamp and said conmanual switch of the self-restoring type, said switch being momentarily closable to energize said transfer relay in parallel with said lamp; and a normally open contact on said transfer relay connected in parallel with said manual switch to complete a locking circuit for said transfer relay upon momentary closing of said switch. 11. In an alarm system as in claim 7, a series circuit at said second station comprising a source of potential, the winding of a master relay and a normally open contact, means for momentarily closing said contact to energize said master relay responsive to energization of said other polarized relay, a locking circuit in parallel with said contact comprising a normally open contact on said master relay in series with a normally closed manual switch of the self-restoring type, and a circuit in parallel with said master relay winding including said switch in series with a signal device.

12. In an alarm system, a series circuit comprising a source of potential, a lamp and a normally open contact, means for at times closing said contact and on each instance maintaining same closed for a variable interval of time, a circuit in parallel with said lamp including an audible signal in series with a normally closed contact, a relay operable to open said last contact, a second circuit in parallel with said lamp including in series the winding of said relay and a normally open switch of the self-restoring type, and a normally open contact on said elay connected in parallel with said switch to complete a locking circuit for said relay upon momentary closing of said switch.

13. In an alarm system, a normally open contact, means for at times closing said contact and in each instance maintaining same closed for a variable interval of time, a relay having a normally closed contact, an alarm, a source of potential, a reversible two-position switch, a circuit completed by said switch in one position thereof, said circuit including in series said source, said switch, said alarm and said first contact; said switch effective in the other position to substitute the winding of said relay for said alarm in said circuit, and an alternate circuit for said alarm completed by said switchin said last position thereof, said alternate circuit including in series said source, said alarm and said relay cont-act.

14. In anjalarm system as in claim 13, a second alarm device, a circuit completed by said switch when in said one position thereof to connect said second alarm device in parallel with said first alarm, and a circuit completed by said switch when in said other position thereoffor "connecting said second alarm device directly in bridge to said source of potential.

15. In a fire alarm system, a central station, a plurality of local stations each having a two-conductor transmission line extending to said central station, each local station having thereat a source of DC. potential normally connected in bridge to that stations transmission line,

'means at each local station for disconnecting said source larized alarm relay connected to that line and energized only upon said reversal of polarity of the DC. source at the associated local station, a master alarm signal and a master trouble signal at said central station, means con trolled jointly by all of said alarm relays and effective to operate said alarm signal responsive to the energization of any of said alarm relays, and means controlled jointly by all of said supervisory relays and efiective to operate said'trouble signal responsive to the release of any of said supervisory relays.

16. In a fire alarm system, a central station, a plurality of local stations each having a two conductor transmission line extending to said central station, each local station having thereat a source of DC. potential normally con nected in bridge to that stations transmission line, means at each local station for disconnecting said source from t e l e in the vent of a local circuit fault condition,

21 otherfmeans at each local station for reversing the polarity of the D .C'. potential connected to that stations transmission line in the event of a local alarm condition, said centralstation having, for each transmission line, apolarized supervisor-y relay connected to that line and normally energized by said DC. potential connected thereto at the associated local station, said central station also having, for each transmission line, an oppositely polarized alarm relay connected to that line and energized only upon said reversal of polarity of the DC. source at the associated local station, a master alarm signal at said central station, means controlled jointly by all of said alarm relays and efiective tooperate said alarm signal responsive to energization of any of said alarm relays, a mastertrouble lamp at said central station, means controlled jointly by all of said supervisory relays and effective, responsive to the release of any one thereof, to connect asource of potential'to said lamp to light same, a circuit in parallel with said lamp including an audible signal in series with a normally closed contact, a transfer relay adapted to open said last contact, a second circuit in parallel with said lamp including in series the winding of said transfer relay and a normally open manual switch of the selfrestoring'type, said switch being momentarily closeable to energize said transfer relay in parallel with said lamp, and a normally open contact on said transfer relay connected in parallel withisaid' manual switchctoi complete a lockingcircuit'for said transfer relay uponmomentary closingof said switch.

17 L In a fire alarm system, a central station, a plurality of local stations eachhaving a two-conductor transmission lineextending to said central station,,each'localstation having thereat-a source of DJC. potential normally connected in bridge to that stations, transmission line, means at'each local station for disconnecting said' source from the line in the event of a local circuit fault condition, other means. at each local station for reversing the polarity'of the 13.0. potential connected tothat stations transmission line'in the eventiofa local alarm condition,

said centralstation having, for each transmission line, a polarized supervisory relay connected to that line and normally energized: by said DC. potential connected thereto at theassociated local station, saidcentral station also. having, foreach transmission line, an oppositely p0:

contact on said master relay inserie's with a normally in" parallel with said master relay including a switch-in series with a master alarm signal device, a mastertrouble signal device at said central station-,andrmeans controlled closedmanual switch ofv the self-restoring type, a circuit nected thereto atsaid originating station, said receiving station also; having thereat an oppositely polarized alarmrelay' connected to the line and energized only upon said reversal of polarity of the D0. source at said originating station, a master alarm signal and a master trouble signal at said receiving station, means controlled by said alarm relay to operate said master alarm signal responsive to energization ofvsaid alarm relay, and means controlled by said supervisory relay to operate said master trouble signal responsive to release of said supervisory relay.

19. In a fire alarm system, an originating station having local circuits for detecting alarm conditions, a remote receiving station; a two-conductor transmission line extending from said originating station to said receiving station, said orignatingstation having thereat a source of DC. potential normally connected in bridge. to said transmission line, means at said originating station for disconnecting said source from the line in the event of a local circuit fault condition, other means atsaid originating station for reversing the polarity of the D.C. potential connected to said transmission line in the event of an alarm condition, said remote receiving station having thereat a polarized supervisory relay connected to the line and normally energized by the DC. potential connectedthereto at said originating station, said receiving station also having thereat an oppositely polarized alarm relay connected to the line and energized only upon said reversal of polarity of the DC. source at said originatingstation, a master alarm signal at said receiving station, 'rneanscontrolled by said alarm relay to operate said masteralarm signalresponsive to energization of said alarm relay, a master t'roublelarnp at saidreceiving station, means controlled by said supervisory relay responsive to release thereof to-connect a source of potential to said-lamp-tolight same, a circuit in parallel with said lamp including an audible signal in series with a normally closed contact, a transfer relay adapted to' open said last contact, 'a second circuit in parallel with said lamp including in series the winding of said transfer relay'and a normally open manual switch of the selfrestoringtype, said switch being momentarily closeable to energize said transfer relay in parallel Withsaid lamp, and a normally open contact on said transfer relay connected in parallel with said manual switch to complete a locking circuit for said transfer relay upon momentary closing of said-switch.

2.0. Ina fire-alarm system, anoriginating station having local-'circu-its for detecting alarm conditions, a remote receiving station, a two-conductor transmission line extending from said originating station to said receiving station, said originating station having thereat a source of D.C. potential normally connectedin bridge to said transmission line, means at said originating station-for disconnecting said source from the line in the 7 event of a local circuit fault condition, other means at jointly byall" of, said supervisory relays, and effective to operate said trouble signal de'vicerresponsive? to the release of any of said supervisory relays.

18. In a fire alarm system, an originating station hav-' ing local circuits for detecting alarm conditions, a remote receiving station, a two-conductor transmission line extending from said originating station to said receiving station, said originating'station having thereat a source of DC. potential normally connected in'bridge to said transmission line, means at said originating station for disconnecting said source from the line in the event of a local circuit fault condition, other means at said originating station for reversing the polarity of the DC. potential connected to said transmission line in the event of an alarm condition, said remote receiving station having thereat a polarized supervisory relay connected to the 'line and normally energized by the D.C. potential'consaidloriginating station for reversing the'polarity of the stat-ion having thereat a polarized supervisory relay connected to the line andnormally energized by the-11C.

' potential connected thereto, at said originating station,

winding of a master relay and a normally open contact,

means controlled by said alarm relay to momentarily close said contact responsive to energization of said alarmrelay, a locking circuit in parallel with said contact comprising a normally open contact on said master relay in series with a normally closed manual switch of the self-restoring type, a circuit in parallel with s'aid master relay including a switch in series with a master alarm,

signal .device, a master trouble signal device at said receiving station, and means controlled by said supervisory relay to operate said master trouble signal device responsive to release of said supervisory relay.

21. In a self-supervising alarm system of the type described, a central panel, a plurality of external loops each comprising a two-conductor detection line extending from said panel so that it passes through a portion of the protected premises and then returns to the panel, each of said two-conductor lines having an individual supervisory relay normally connected in bridge to that line at one end thereof, each of said two-conductor lines having at the other end thereof a circuit connected in bridge to the line, said circuit comprising a source of potential in series with an alarm relay individual to the line, the supervisory relay for each line normally being energized over the line from said source and the alarm relay for each line being marginal whereby it cannot operate in series with that lines supervisory relay, the portion of each two-conductor line outside said panel being bridged by one or more normally open contacts capable of being closed thereby to simultaneously operate the alarm relay and release the supervisory relay for that line, each line having an alarm signal individual to that line, means controlled by each lines alarm relay for operating that lines alarm signal responsive to operation of said relay, and means controlled by each lines supervisory relay for operating that lines supervisory signal responsive to release of said supervisory relay.

22. An alarm system as in claim 21 wherein said panel has a master alarm signal and a master trouble signal common to said lines, means controlled jointly by all' of said alarm relays and effective to operate said master alarm signal responsive to operation of any of said alarm relays, and means controlled jointly by all of said supervisory relays and eflfective to operate said master trouble signal responsive to the release of any of said supervisory relays.

23. In a self-supervising alarm system of the type described, a central panel, a plurality of external loops each comprising a two-conductor detection line extending from said panel so that it passes through a portion of the protected premises and then returns to the panel, each of said two-conductor lines having an individual supervisory relay normally connected in bridge to that line at one end thereof, each of said two-conductor lines having at the other end thereof a circuit connected in bridge to the line, said circuit comprising a source of potential in series with an alarm relay individual to the line, the supervisory relay for each line normally being energized over the line from said source and the alarm relay for each line being marginal whereby it cannot operate in series with that lines supervisory relay, the portion of each two-conductor line outside said panel being bridged by one or more normally open contacts capable of being closed thereby to simultaneously operate the alarm relay and release the supervisory relay for that line, said panel having a master alarm signal and a master trouble signal common to said lines, means controlled jointly by all of .said alarm relays and effective to operate said ,master alarm signal responsive to operation of any of said alarm of said detection circuits.

relays, and means controlled jointly by all of said supervisory relays and effective to operate said master trouble signal responsive to the release of any of said supervisory relays.

24. An alarm system as in claim 23 wherein said means controlled jointly by said alarm relays comprises a master alarm relay and wherein said means controlled jointly by said supervisory relays comprises a master trouble relay, said master alarm relay having means effective upon operation thereof to connect said source of potential to said master trouble relay thereby to operate the latter, and said trouble relay effective when operated either by said master alarm relay or by said supervisory relays to connect said source to said master trouble signal to operate said signal.

25. In a zoned alarm system of the type wherein each zone has an individual alarm relay arranged to operate whenever there is an alarm condition on the detection circuit for that particular zone, and wherein each zone also has an individual normally operated supervisory relay arranged to release whenever there is a fault condition on that particular 'zones detection circuit; the improvement which comprises a master alarm relay and a master trouble relay common to all of said zones, a source of potential, each of said individual alarm relays having means effective upon operation of that relay to connect said source to said master alarm relay, whereby the latter is operated by one of said individual alarm relays whenever there is an alarm condition on any of said detect-ion circuits, each supervisory relay having means effective upon operation of that relay to connect said source to said master trouble relay, whereby the latter is operated by one of said supervisory relays whenever there is a fault condition on any of said detection circuits, means controlled by said master :alarm relay upon operation to connect said sources to said trouble relay whereby said trouble relay also is operated whenever there is an alarm condition on any of said detection circuits, an

alarm signal and a trouble signal also common to all of said zones, means controlled by said master alarm relay upon operation to connect said source to said alarm signal whereby the latter is operated whenever there is an alarm condition on any of said detection circuits, and means controlled by said master trouble relay upon operation to connect said source to said trouble signal whereby said trouble signal is operated whenever there is either an alarm condition or a fault condition ion any References Cited in the file of this patent UNITED STATES PATENTS, 2,000,074 Grant May 1935 2,127,343 Parlett Aug. '16, 1938 2,278,939 Muehter Apr. 7, 1942 2,420,481 Jackson et al. May 13, 1947 2,493,548 Proctor a Ian. 3, 1950 2,565,323 Quinn Aug. 21, 1951 2,712,129 'Marmorstone June 28, 1955 2,713,157 Collins July 12, 1955 2,731,627 Herbst Jan. 17, 1956 

